A controversial American Christian group has renounced its campaigning position that homosexuality can be "cured" through prayer.

Exodus International, which has 260 ministries around the United States and the world, has been vigorously opposed by gay rights activists for decades.

It claims to have helped tens of thousands of people rid themselves of unwanted homosexual inclinations through a process variously known as "conversion," "reparative," or "ex-gay" therapy.

The group used the slogan "Change is possible" and suggested that homosexuality was a choice, an argument used by conservative Christian groups to oppose same-sex marriage.

But the organisation's president Alan Chambers has now abandoned the stance. He said: "I do not believe that 'cure' is a word that is applicable to really any struggle, homosexuality included."

Mr Chambers, who is married to a woman but talks openly about his own sexual attraction to men, added: "For someone to put out a shingle and say 'I can cure homosexuality,' that to me is as bizarre as someone saying they can cure any other common temptation or struggle that anyone faces on Planet Earth."

He said "99.9 per cent" of people he had encountered in two decades with Exodus were not able to completely rid themselves of same-sex attraction.

His comments have caused a rift in the organisation's own ranks with 11 of its ministries defecting. One opponent accused Mr Chambers of dropping his campaign because he was "tired of his own personal struggles."

And Robert Gagnon, an associate professor at the Pittsburgh Theological Seminary, called for Mr Chambers to resign. He told the New York Times: "My greatest concern has to do with Alan's repeated assurances to homosexually active 'gay Christians' that they will be with him in heaven."

Wayne Besen, a Vermont-based activist who has worked to discredit ex-gay therapy, said: "We appreciate any step toward open, transparent honesty that will do less harm to people.

"But the underlying belief is still that homosexuals are sexually broken, that something underlying is broken and needs to be fixed. That's incredibly harmful, it scars people."

The California state senate passed a bill to ban reparative therapy for minors last month and other states may follow.